Rinse the blueberries and have them ready. No muddy soup please — quick pat-dry if needed.

In a heavy-bottomed pot, combine blueberries, sugar, lemon juice, lemon zest (if using), salt, and water. Stir to coat everything evenly.

Cook over medium heat, bringing the mixture to a gentle simmer. Stir occasionally to keep it from sticking and scorching.

As it cooks, chips of blueberry will burst and the sauce will thicken. If you like it chunkier, mash a few berries with the back of a spoon.

Boil for about 10–15 minutes, until the jam coats the back of a spoon. If you want a thinner jam, cook a little less; for a thicker jam, give it a few more minutes.

Test the gel point on a cold plate: a small drop should wrinkle when you push it. If not, simmer 1–2 minutes longer and retest.

Remove from heat and let cool slightly. Spoon into clean jars and seal. Chill in the fridge or process for longer storage if you’re into canning.